President Donald Trump is meeting with NATO Secretary General Jens Stoltenberg (yehnz STOHL'-tehn-burg) at the start of a summit of the military alliance.
Trump is expected to continue questioning wary NATO allies about their military spending during talks in Brussels.
He tweeted en route from Washington that European counties "want us to happily defend them through NATO, and nicely pay for it. Just doesn't work!"
Trump's day will include a welcome ceremony, a meeting of the North Atlantic Council and a working dinner with some of the same leaders he berated over trade during his last world leaders' summit in Canada last month.
Brussels is the first stop of a week-long European tour that will include stops in the United Kingdom and a meeting with Russia's Vladimir Putin.